1. Field of the Invention
The present invention relates to a holding table for holding a platelike workpiece such as a wafer.
2. Description of the Related Art
A processing apparatus such as a grinding apparatus, cutting apparatus, and laser processing apparatus for processing a platelike workpiece such as a wafer includes a holding table (chuck table) having a holding surface for holding the platelike workpiece under suction as disclosed in Japanese Patent Laid-open No. Hei 5-23941 and Japanese Patent Laid-open No. 2008-140832, for example. In processing the workpiece held on the holding table under suction, there is a possibility that contaminants may adhere to the contact surface of the workpiece which comes into contact with the holding surface of the holding table.
As a result, there is a possibility that the contaminants adhering to the workpiece may contaminate a transporting unit for transporting the workpiece or contaminate the inside of a cassette for storing the workpiece after processing. When a clean workpiece is transported by the transporting unit once contaminated or stored into the cassette once contaminated, there is a possibility that the clean workpiece may also be contaminated. As disclosed in Japanese Patent Laid-open No. 2004-107606, there is a case that a platelike workpiece is attached through an adhesive or wax to a support plate in order to facilitate the handling of the workpiece. Further, as disclosed in Japanese Patent Laid-open No. 5-21763, there is widely used a technique of directly bonding a workpiece to a support plate.